Conventional magnetic disk drives are information storage devices which utilize at least one rotatable magnetic media disk with concentric data tracks, a read/write transducer for reading and writing data on the various tracks or separate read and write tranducers as in the magnetoresistive and giant magnetoresistive heads which have become the trend in the data storage industry as a means of improving data storage density. Disk drives generally also have an air bearing slider for holding the transducer adjacent to the track generally in a flying mode above the media, a suspension for resiliently holding the slider and the transducer over the data tracks, and a positioning actuator connected to the suspension for moving the transducer across the media to the desired data track and maintaining the transducer over the data track during a read or a write operation.
The recording density of a magnetic disk drive is limited by the distance between the transducer and the magnetic media. One goal of air bearing slider design is to "fly" a slider as closely as possible to a magnetic medium while avoiding physical impact with the medium. Smaller spacings, or "fly heights", are desired so that the transducer can distinguish between the magnetic fields emanating from closely spaced regions on the disk.
In addition to achieving a small average spacing between the disk and the transducer, it is also critical that a slider fly at a relatively constant height. The large variety of conditions that transducers experience during the normal operation of a disk drive can make constancy of fly height anything but a given. If the flying height is not constant, the data transfer between the transducer and the recording medium may be adversely affected.
The manner in which a slider is manufactured and the material the slider is fabricated from can affect fly height. Preferably variations in the physical characteristics of the slider, e.g. due to manufacturing tolerances, should not substantially alter the flying height of the slider. If this result is not achieved, the slider's nominal fly height must be increased to compensate for variations between sliders.
The current process for defining air bearing surfaces uses a dry-film resist as the etch mask. Most current air bearing surface designs are patterned using only a single etch. However, for improved fly height control designs may be patterned using dual etch processes. To process multiple etch designs, an ion milling step and a reactive ion etching step may be used for either of both steps. At certain row spacings the ion milling etch results in redeposited materials being formed on the sides of the rows which cannot be removed. In addition, the etch profiles obtained after ion milling and reactive ion etching steps have shallow wall profiles which make inspection difficult and affect the flying characteristics of the slider.
Exemplary processes used in forming sliders include, Hinkel, et al., U.S. Pat. No. 4,624,048 which discloses a method for making magnetic head sliders using a mask that leaves the area of the substrate surface intended for forming the rails uncovered. Hinkel, et al. uses chemical wet etching to define the recessed regions between respective rails using oxide formed on the surface of the aluminum in the exposed regions as an etch mask.
Carr, et al., U.S. Pat. No. 5,617,273 discloses formation of a thin film slider having a protruding read/write element formed by chemical-mechanical polishing. Carr, et al. uses a lapping slurry to erode the substrate and insulator at a rate which is different than the rate of erosion for the read/write component. The resulting read/write components protrude from the insulator. Slade, et al., U.S. Pat. No. 5,613,293 discloses a method for providing a smooth topographical interface between head and disk surfaces through the use of photoresist etching processes.
Kojima, et al., U.S. Pat. No. 5,548,886 also discloses a method for manufacturing floating magnetic head devices. The process includes forming a resist mask having a predetermined slider surface shape onto a substrate and injection of a solid/gaseous two-phase current of free abrasive grains through an injection nozzle.
Kemp, U.S. Pat. No. 5,516,704 also discloses a method for manufacturing magnetic head air bearing sliders by forming transverse pressure contours on the edges of the slider air bearing surface. Kemp forms these contours by first forming slots in the slider blank adjacent the location where the air bearing surfaces are to be formed. The slots are then filled with an etchable material and the slider blank is machined to form air bearing structures. The etchable material is positioned to form a part of the slide edge of the air bearing structure. The slider blank is then subjected to an etching process that principally etches the etchable material.
Hussinger, U.S. Pat. No. 5,516,430 discloses a planarization procedure which uses an alignment fixture on which the rows are temporarily fixed with pins. A filled thermoplastic material is then placed on the rows with a substrate on top. The substrate is heated to 400-500.degree. F. causing the encapsulant to melt and flow into the gaps between the rows. The heating process is controlled by maintaining the alignment fixture near ambient temperature to avoid encapsulant sticking to the fixture. Sufficient heat is applied to melt the material near the air bearing surface (ABS) which may contain thermally sensitive transducers.
The potential for seepage of material onto the air bearing surface on the slider is a concern using the Hussinger process. The presence of tapers at the leading edge of the slider provide a conduit by which the material can reach the ABS. Contamination of the ABS also causes photoresist imaging and adhesion problems.
Another problem with the Hussinger procedure is the presence of the pins in the alignment fixture. These features will cause holes to exist in the encapsulated carrier. The holes will contribute to yield loss since sliders near holes will be subjected to redeposition during etch steps. Furthermore, the high temperature requirement for this procedure (400-500.degree. F.) may preclude use of certain thermally sensitive transducers such as giant magnetoresistive sensors which are used to produce higher density magnetic storage products.
As a result, there is a continuing need for processes and apparatus which will provide sliders having air-bearing surfaces formed by patterned etching with reduced redeposition of etched particles and finer etch patterns